This invention relates to a curtain control system for animal enclosures such as poultry houses. Houses of this type and prior art systems for controlling ventilation and preventing or reducing animal mortality during power interruptions and extremely warm weather are disclosed in applicants' prior U.S. Pat. Nos. 3,915,377, 4,113,175, 4,428,278, and 4,986,469. Systems such as shown in these prior patents have substantially reduced animal mortality and labor requirements for raising poultry in large, environmentally controlled enclosures. Nevertheless, on some occasions inadvertent release of the some of the curtains can cause environmental conditions resulting in stress and mortality to the animals.
As poultry houses have become larger and more environmentally controlled, the sides of the enclosure are sometimes divided into two or four separate curtain units, with each unit having its own curtain release device. Since all of these units are designed to release when electric current is interrupted, all of the curtains should drop into their open position to permit natural ventilation during any power interruption.
In an poultry house having so-called "tunnel" ventilation, an interruption of electrical power or high temperature causes the curtain winches to be released and the curtains to drop. However, it can happen that power is restored or the temperature drops before all of the curtains release. In some other instances, one or more of the curtains may be inadvertently dropped, with the remainder of the curtains left in their raised, closed position. In both of these instances the flow of air is short-circuited. Air flow through the enclosure moves from the open curtain area in a direct path to the ventilation fans, bypassing other areas of the enclosure. Poultry in the bypassed areas are deprived of adequate air flow and consequently suffer. In this instance, the poultry would be better off if all of the curtains had inadvertently dropped, rather than just some of them.
Some systems have motorized curtain systems which operate to close the curtains when the enclosure changes from natural ventilation to fan-powered tunnel ventilation. In some instances the curtains or the cords operating the curtains may bind or snag, thus increasing the pull on the winch handle which is held in place with a curtain release device. If the curtain release device fails to hold, the particular set of curtains is released, again causing a short circuit in the air flow path. Animals out of the path of air flow suffer from loss of fresh air, increased temperature, and lack of air movement.
Prior art systems do not provide a method and apparatus for insuring the positive release of all of the sets of curtains when any one set of curtains is released. The invention disclosed in this application and claimed in the claims accomplishes this new function.